Can't access editing tools in layout workspace
You seem to have unvoluntarily disabled Viewport overlays and gizmos (these are all the contour lines, widgets, grids, basically everything that is not renderable geometry). To re-enable them, press these buttons in the top-right corner of your 3D viewport:



The little arrows next to them let you selectively enable/disable elements.

If that's not your issue, maybe it is that you want to enter the Edit Mode?

There are 3 ways to access it:


On the top-left corner of your screenshot, you can see 'Object Mode'. Click on it and select Edit Mode
While your cursor is on the 3D Viewport and your object(s) is/are selected, hit Ctrl + tab. A pie menu appears: select Edit Mode
Still while your cursor is on the 3D Viewport, hit the tab key : it toggles between Edit and Object mode